Hi. I just want some advices to troubleshoot an issue that we have with a CISCO2951/K9. It connects to Internet through the GigabitEthernet0/1 interface. Since a few days ago, the Gi0/1 interface is flapping many times in a day:
100468: Oct 30 12:16:28 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
100469: Oct 30 12:16:29 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
100474: Oct 30 12:17:08 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
100475: Oct 30 12:17:09 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
100468: Oct 30 12:16:28 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
100469: Oct 30 12:16:29 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
100474: Oct 30 12:17:08 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
100475: Oct 30 12:17:09 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
We created an eem applet, that captures the "show clock" and "show interface gi0/1" commands as soon as the interface goes down. These are the results:
Roluter# show interf gi0/1
GigabitEthernet0/1 is down, line protocol is down
Hardware is PQ3_TSEC, address is 649e.f339.9a01 (bia 649e.f339.9a01)
Internet address is 192.168.1.75/24
MTU 1500 bytes, BW 20480 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Auto Duplex, Auto Speed, media type is unknown media type
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:22, output 00:00:02, output hang never
Last clearing of "show interface" counters 1d15h
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 6
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1330212 packets input, 1339056636 bytes, 0 no buffer
Received 8648 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
874555 packets output, 104159044 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
7 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
It seems it might be a cable issue, since it is showing "7 lost carrier" and CISCO says:
| no carrier | Description: Cisco IOS sh interfaces counter. The number of times the carrier was not present in the transmission. Common Causes: Check for a bad cable. Check the physical connection on both sides. |
Nevertheless, we are managing this router remotely, because it is located at other city; and we don't know how to troubleshoot this issue.
What reasons could be creating the flapping? Could it be a Internet provider issue? Could it be the cable on the Gi0/1 interface? A modem issue? What is the most common reason to the "lost carrier" log?
Please, we need to solve this problem, and as I said before, we are managing it remotely, so we don't have physical access to it.
Thank you very much.
Fabio
